Hypertension is believed to be one of the major causes of end stage renal disease (ESRD) in the general population and the number one cause in African Americans. Despite the availability of potent antihypertensive drugs, the number of hypertensive African Americans progressing to ESRD continues to rise. This disproportionately high prevalence of ESRD in African Americans cannot be explained by the higher prevalence of hypertension, per se. Whether this is a result of increased susceptibility of the African American kidney to hypertensive injury or because of the concurrent existence of unidentified renal factors is not known. There is some preliminary evidence suggesting that some antihypertensive drugs may retard the progression of hypertensive renal disease, but no clinical trial has been conducted to test this hypothesis in African Americans. This multi-center project will, therefore, try to answer the following questions: 1) Is the pathological lesion in "hypertensive renal disease" purely a result of persistent hypertension? 2) Is one antihypertensive drug better than another in terms of preservation of renal function? 3) Is there a level of blood pressure (BP) more suitable for the survival of the kidney as opposed to the generally recommended level of 140/90mmHg? To this effect, hypertensive African Americans between the ages of 18-70 years old and with no other known disease that can affect the kidney will undergo BP screening and glomerular filtration rate (GFR) tests. Those who qualify, based on BP levels and the GFR results, will then be randomized, in double-blind fashion, to one of the three major antihypertensive classes (angiotensin converting enzyme inhibitor, calcium channel blocker, or beta blocker) and to one of two levels of mean BP (less than or equal to 92mmHg or 102- 107mmHg). Other antihypertensive drugs will be added to keep the BP at the desired level. The BP levels of the randomized subjects will be monitored on a regular basis and compliance to medication(s) checked simultaneously. Renal function also will be traced with periodic GFR tests throughout the study period, which will last approximately four years. All data will be collected and sent to the Data Coordinating Center (DCC) for analyses and interpretation. It is hoped that the results of the African American Study of Kidney Disease and Hypertension (AASK) Full Scale Trial will shed some light on the physiopathology of hypertensive renal disease that has remained a mystery so far, and that we will be able to develop some guidelines to prevent the ever increasing prevalence of ESRD in African Americans.